Despite surgical advances in the early repair of congenital cardiac malformations that cause overloading of pulmonary circulation, the palliative procedure referred to as "Pulmonary Artery Banding" is still performed on several thousand children each year. The procedure is often performed where the cardiac malformations are so complex that staged surgeries are required. The procedure is also performed in cases where, because of the age of the infant, final repair of the anomaly would pose too high a risk of mortality.
Pulmonary Artery Banding is a palliative procedure designed to reduce blood flow through the pulmonary artery, so as to reduce distal pulmonary artery pressure. The procedure is effective in alleviating congestive cardiac failure and protects the pulmonary vasculature from experiencing irreversible increases in hemodynamic resistance. Pulmonary Artery Banding is typically performed through a thoracotomy, and involves placing a band formed from a cotton umbilical tape, woven Dacron.RTM. tape, or other material, around the main pulmonary artery. The band is then tightened to constrict the pulmonary artery to a desired diameter.
While Pulmonary Artery Banding presents a relatively low risk of mortality, about 3-5%, it nevertheless has a number of disadvantages and drawbacks. Primary among these drawbacks is the inability of the surgeon performing the procedure to assess, from the hemodynamic standpoint, the optimal final diameter to which the pulmonary artery should be adjusted. Often, the surgeon must rely upon his or her experience in adjusting the band to achieve acceptable forward flow (i.e., to sustain a forward cardiac output), while decreasing the blood flow sufficiently to protect the pulmonary vasculature.
Moreover, there is a risk that the band will erode through the pulmonary artery, thereby causing vessel thrombosis or hemorrhage. It is also not uncommon for the band to migrate towards one of the main pulmonary branches (usually the left), resulting in stenosis of the origin of the other main pulmonary branch (usually the right). In addition, the band must be removed in a subsequent operation, for example, when the malformation is corrected.
Edmunds et al. U.S. Pat. No. 3,730,186 describes an implantable pulmonary artery band including a toroidal balloon occluder that is disposed around the native pulmonary artery. The balloon occluder is inflated via a subcutaneously implanted injection button using a conventional hypodermic needle. A drawback of the Edmunds et al. device is the relative complexity of the device and the need to eventually remove the device once the congenital malformation is corrected.
In view of the foregoing, it would be desirable to provide a relatively simple device for selectively adjusting blood flow through a vessel.
It further would be desirable to provide apparatus and methods suited for percutaneous transluminal delivery of a device for selectively adjusting blood flow through a vessel.
It further would be desirable to provide methods that permit adjustment of the device with reduced trauma to the patient and cost relative to previously known methods.